159 



oxygen ; and that, although insects will live a con- 

 siderable time in this gas, yet their breathing be- 

 comes oppressive, and they die (3.) long before 

 the whole of it is consumed. There can be little 

 doubt but that the other classes of inferior animals 

 would, under the same circumstances, suffer in the 

 same manner. In the experiment also made by 

 Lavoisier on the guinea pig (122.), the animal is 

 said to have breathed with much difficulty, although 

 not more than one-fifth of the oxygen gas was consu- 

 med : but some experiments of the same author, at 

 a later period, seem in opposition to this fact. In 

 comparing together the phenomena of combustion 

 and respiration, he observes, that much more com- 

 bustible matter is consumed in a given time in vital 

 air, than in that of the atmosphere, but that the 

 same circumstance does not hold in respiration : 

 for whether animals respire oxygen gas in its pure 

 state, or mixed with a proportion, more or less con- 

 siderable, of nitrogen gas, the quantity of oxygen 

 which they consume is always the same. If a gui- 

 nea pig, he adds, be kept for several days in oxygen 

 gas, or in a mixture composed of fifteen parts ni- 

 trogen and one of oxygen, preserving constantly 

 these proportions, the animal in both cases conti- 

 nues in his natural state : his respiration and circu- 

 lation do not sensibly appear to be either accelerated 

 or retarded : his temperature remains the same, ar^d 

 he has only, when the proportion of nitrogen ga's is 

 too great, a slight disposition to drowsiness *, 



* Mem. Acad. 1789. 



